The present invention relates to a new and improved closure mechanism or device for an injection molding machine or extrusion press.
Injection molding machines and extrusion presses for the fabrication of plastic parts or parts formed of light metals possess a closure mechanism incorporating a stationary tool support and a displaceable tool support. At each of both tool supports there is clamped or otherwise affixed a respective part of the molding tool or mold. During the fabrication of a molded part the displaceable tool support is displaced towards the stationary tool support during a first working step, until both tool parts contact one another and the molding tool is closed. In the next working step the molding mass which is to be processed is expressed into the tool or mold. Following the pressing-in of the molding mass is a cooling step or phase during which time the molding mass or compound solidifies. Thereafter the displaceable tool support is again moved away from the fixed tool support and the molding tool or mold is thus opened, so that the fabricated molded part can be ejected.
With prior art closure devices the non-displaceable tool support was rigidly connected with a number of rods which are in parallelism with one another, the so-called press struts or columns, along which there can be displaced the displaceable tool support or carrier. The latter is connected with the piston of a hydraulic cylinder.
In order to maintain the molding tool closed during the pressing-in of the molding mass the piston must transmit a very large force to the displaceable tool support. This force can amount to approximately 1 million kiloponds or more for machines of average size. Due to the play of the movable elements or due to small deformations there can be brought about canting and binding, by virtue of which the press struts are subjected to large forces. These forces can become so great that the press struts are destroyed.
A further drawback of the state-of-the-art closure mechanisms resides in the fact that for the attachment of the hydraulic cylinder at the side of the displaceable tool support, and which side faces away from the stationary tool support, there is required a special carrier or support. This has a result that the press struts must be very long in order to realize a satisfactory stroke. Consequently, the closure mechanism becomes very large and expensive.